This invention relates to the application of adhesive to molded plastic components which may, for example, be covered with a decorative fabric. A typical component is a plastic pillar located adjacent the foldable back seat of a station wagon. To improve the appearance of the pillar, its exposed surfaces are covered, either partially or entirely, with fabric which is adhesively secured to the plastic.
Previously, most vehicle trim components have been molded of ABS plastic which readily lends itself to use with adhesive but which is relatively expensive. Polymer materials such as polyethylene and polypropylene are significantly less costly but, due to their non-polar chemical structure, do not bond well to adhesives. As a result, it has been necessary to surface treat such materials to increase the wetability of their surfaces.
It is known to treat the surfaces of components made of thermoplastic olefins by means of a high voltage discharge created by moving an electrode along a predetermined path. For example, Manabe et al. U.S. Pat. No. 4,836,901 discloses an electrode which is moved along multiple axes by the arm of an industrial robot and which acts to surface treat those areas of the component where adhesive is subsequently applied. The Manabe et al. system, however, is relatively complex and, if used in an automated production line, would require one manufacturing station to be dedicated to surface treatment and a separate station to the application of adhesive. Moreover, in the Manabe et al. system, the electrode which is carried by the robot arm is at high voltage and thus special insulation and mounting arrangements are required in order to eliminate or minimize discharge between the electrode and the generally electrically grounded components of the robot. Also, routing of an unsheathed high voltage cable to the electrode may require special insulating stand-offs to prevent the cable from contacting grounded components of the robot and may interfere with freedom of movement of the robot arm. Although it is known to apply the high voltage to a stationary jig, while maintaining a discharge electrode at ground so as to minimize insulation of the robot, such system still necessitates the use of a separate station for the application of adhesives.